De-clicker settings - muffled sound?

The Audacity de-clicker is threshold-dependent, so you need to normalize first …
Step #1. RMS normalize to -18dB.
Step #2. (Soft) limit to -3dB, 10ms hold, no make-up gain.
Step #3. Use the de-clicker settings below …

declicker-suggested-settings .png
Optional: an expander plugin, like couture, to attenuate the faint hiss between phrases.

BTW I think you’re a bit too close to the mic: it’s rattling in places from the loudness of your voice.